Rubber-coated stainless steel is generally distributed as a gasket material for vehicular engines. For example, JP-A-3-227622 discloses a gasket material composed of a stainless steel plate having on one or both sides thereof a chromate film comprising a chromium compound, phosphoric acid and silica and a rubber layer applied on the chromate film.
Such a gasket material having a rubber layer on a chromate-treated stainless steel plate exhibits improved performance such as heat resistance and adhesion in antifreeze. However, the recent enhanced consciousness of environmental conservation has been boosting the tendency to avoid chromate treatment because hexavalent chromium contained in a chromate treating liquid directly gives adverse influences to human body. Besides, waste liquid containing hexavalent chromium must be subjected to special treatment as regulated in Water Pollution Control Law (Japan), and scrap of chromate-treated stainless steel is not recyclable. Additionally, there is high possibility that chromium is extracted from the chromate film in contact with antifreeze or oil.